Tests conducted by the Arkansas Department of Health (ADH) found biological contamination in certain lots of Mountain Pure bottled water this week. The company has issued a voluntary recall of those lots, WPEC-CBS12[7] reported.

The affected lots have a four-digit time code between 2200 and 0400 and have a an expiration date of that says either “Best By 2-27-2013 MPWA” or “Best By 2-28-2013 MPWS.” The bottles are the 16.9-oz size.

The contaminated samples were taken from a shipment of bottled water sent to Clinton, Ark., which is under a boil alert due to the recent flooding.

Further testing will reveal the type of mold contaminating the water and its origin. According to ADH officials, healthy people are unlikely to become ill from consuming the water, but it would affect those with weakened immune systems.